1. Field of the Invention
The present invention relates to a method of producing a polyester using a microorganism.
2. Related Background Art
So far, it has been reported that a variety of microorganisms produce poly(3-hydroxybutyrate) (hereinafter, abbreviated as PHB) or other polyhydroxyalkanoates (PHA) and store it in their bodies (“Biodegradable plastic handbook”, Biodegradable Plastic Study Associate edition, N.T.S Co., Ltd., pp. 178-197, 1995). These polymers can be utilized for production of various types of products by melt processing or the like, as is the case with conventional plastics. Further, they are biodegradable and therefore have an advantage that they can completely be decomposed by microorganisms in nature, and unlike conventional many synthetic polymeric compounds, they do not remain in natural environments to cause environmental pollution and may not generate harmful substances such as dioxins, endocrine disrupting chemical substances, etc. since they are not required to be incinerated. Furthermore, they are excellent in biocompatibility and highly expected to be applied to the use as soft members for medical care (Japanese Patent Application Laid-Open No. 5-000159).
Recently, in the industrial application of such PHA, it has been attempted to extend the diversity in the physicochemical characteristics of PHA by producing PHA composed of units different from common monomer units.
As one of such methods, an attempt has been made to improve the physicochemical properties of PHA by introducing epoxy groups in side chains of PHA and carrying out a crosslinking reaction or chemical modification using the introduction sites as active points.
There is reported in Macromolecules, 31, pp. 1480-1486 (1998) and Journal of Polymer Science: Part A: Polymer Chemistry, 36, pp. 2381-2387 (1998), synthesis of PHA containing epoxy groups in the side chain terminals by culturing Pseudomonas oleovorans in culture media containing sodium octanoate and 10-undecenoic acid as an unsaturated fatty acid in various ratios to produce PHA containing a variety of percentages of units with unsaturated bonds in the terminals of the side chains and then chemically epoxidizing the unsaturated sites with 3-chlorobenzoic acid. Further, there is reported in Journal of Polymer Science: Part A: Polymer Chemistry, 36, pp. 2389-2396 (1998) that a crosslinking reaction of the above described epoxy PHA was carried out with succinic anhydride using 2-ethyl-4-methylimidazole as an initiator.
As described above, in the improvement of the physicochemical properties of PHA, epoxy groups of the side chain terminals are very useful, however, there is no synthesis method other than the chemical epoxidation of the unsaturated sites in the side chain terminals, and such chemical epoxidation requires very complicated operations and has therefore a practical disadvantage in terms of cost.